Infrared experiment on the wall temperature distribution for a particle packed channel with constant heat flux

2001 ◽  
Vol 46 (18) ◽  
pp. 1566-1568 ◽  
Author(s):  
Jianhua Du ◽  
Xuejiao Hu ◽  
Bin Ma ◽  
Wei Wu ◽  
Buxuan Wang
Keyword(s):  
Heat Flux ◽  
Temperature Distribution ◽  
Wall Temperature ◽  
Constant Heat Flux ◽  
Constant Heat

Long Term Simulation of Horizontal Ground Heat Exchanger for Ground Source Heat Pump

2015 ◽  
Author(s):  
Nurullah Kayaci ◽  
Hakan Demir ◽  
Ş. Özgür Atayılmaz ◽  
Özden Ağra
Keyword(s):  
Heat Flux ◽  
Heat Exchanger ◽  
Temperature Distribution ◽  
Boundary Conditions ◽  
Control Volume ◽  
Constant Heat Flux ◽  
Constant Heat ◽  
Ground Source Heat Pumps ◽  
Ground Source

The earth is an energy resource which has more suitable and stable temperatures than air. Ground Source Heat Pumps (GSHPs) were developed to use ground energy for residential heating. The most important part of a GSHP is the Ground Heat Exchanger (GHE) that consists of pipes buried in the soil and is used for transferring heat between the soil and the heat exchanger of the GSHP. Soil composition, density, moisture and burial depth of pipes affect the size of a GHE. There are plenty of works on ground source heat pumps and ground heat exchangers in the literature. Most of the works on ground heat exchangers are based on the heat transfer in the soil and temperature distribution around the coil. Some of the works for thermo-economic optimization of thermal systems are based on thermodynamic cycles. GHEs is commonly sized according to short time (one year or less) simulation algorithms. Variation of soil temperature in long time period is more important and, therefore, long term simulation is required to be assure the performance of the GSHP system. In this study, long time (10 years) simulation for parallel pipe GHE of a GSHP system was performed numerically with dynamical boundary conditions. In the numerical study ANSYS CFD package was used. This package uses a technique based on control volume theory to convert the governing equations to algebraic equations so they can be solved numerically. The control volume technique works by performing the integration of the governing equations about each control volume, and then generates discretization of the equations which conserve each quantity based on control volume. Thermal boundary conditions can be defined in four different types in ANSYS Fluent: Constant heat flux, constant temperature, convection-radiation and convection. In this study, periodic variation of air temperature boundary at upper surface condition is applied, the lateral and bottom surface of the solution domain are defined as adiabatic wall type boundary condition; the pipe inner surface is taken as wall with a constant heat flux. In order to provide the periodic variation of air temperature boundary at upper surface condition a User Defined Function (UDF) was written and interpreted in ANSYS Fluent. Likewise, a UDF was also written to give constant heat flux intermittently for the pipe inner surface. Constant heat flux of 10, 20, 30 W per unit length of pipe used for calculations. Effects of distance between pipes and thermal conductivity on temperature distribution in the soil were investigated. Heat transfer in the soil is time dependent three dimensional heat conduction with dynamical boundary conditions. Temperature distribution in soil were obtained and storage effect of the soil has also been investigated. An optimization methodology based on long term simulation of GHE was suggested.

Mechanism of Convective Heat Transfer of Airflow in Deep Airway

2011 ◽  
Vol 243-249 ◽  
pp. 4998-5002
Author(s):  
Yi Jiang Wang ◽  
Guo Qing Zhou ◽  
Lei Wu ◽  
Yong Lu
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Temperature Distribution ◽  
Convective Heat Transfer ◽  
Convective Heat ◽  
Constant Heat Flux ◽  
Constant Heat ◽  
Mining Depth ◽  
Axial Temperature ◽  
Criterion Equation

With the increase of mining depth, an investigation of the convective heat transfer of airflow in deep airway is urgently required. The velocity and temperature distribution were derived by using the turbulence model for smooth tube. In order to simplify calculation and avoid the complicated calculation of integration, with the help of velocity-temperature distribution analogy, the criterion equation of convective heat transfer was obtained by using the model of constant heat flux. The coefficient of convective heat transfer between airflow and airway was calculated, and criterion correlation of convective heat transfer was regressed according to test data. Test results show that the axial temperature distribution of airflow is linear, which is encouraging agreement with theoretical calculating results. Hence model of constant heat flux is a viable method for studying the convective heat transfer of airflow in deep airway.

scholarly journals A Study of Temperature Distribution and Thermal Stresses in a Hot Rock Due to Rapid Cooling

2020 ◽  
Vol 142 (4) ◽  
Author(s):  
Tran X. Phuoc ◽  
Mehrdad Massoudi ◽  
Ping Wang ◽  
Mark L. McKoy
Keyword(s):  
Heat Flux ◽  
Temperature Distribution ◽  
Thermal Stresses ◽  
Initial Temperature ◽  
Constant Heat Flux ◽  
Surface Heat ◽  
Uniform Temperature ◽  
Constant Heat ◽  
Thermoelastic Response ◽  
Unit Depth

Abstract Thermal stresses may be induced in a hot dry rock when a cold fluid is injected in the well. To study this problem, we look at the thermoelastic response of a hot rock that is suddenly cooled. The cooling is assumed to be either at a constant temperature or at a constant heat flux per unit depth. Our approach is to nondimensionalize the equations and perform a parametric study and look at the temperature distribution and the induced-thermal stresses. The results indicate that depending on the extent of cooling and the cooling time, thermal stresses can be induced. Numerical simulations on sandstone, with an initial uniform temperature of 473 K, are also carried out. The results show that if the cooling is due to the surface temperature maintained at 463 K (10 °C lower than the initial temperature of the hot rock), thermal stresses that are larger than the rock tensile strength could be induced. When the cooling is due to a constant surface heat flux, this temperature can be reached after about 777 days of cooling with a minimum value of a heat flux of −20 W/m.

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